Why do we get voltage drop across the loads in the parallel circuit in a series-parallel circuit(combination circuit) with an open neutral?

 

Don't understand the question. Post a circuit diagram.

 

Here is a diagram. Excuse the mess

 

What is connected to the duplex outlet labeled "D" ?
What is the L1 to L2 voltage as measured with a voltmeter?

There is a complete current path between L1 and L2. The neutral open causes that.